The present invention relates to radar transmitters and receivers and, more particularly, to the transmission and reception of spectral components of a predetermined train of short pulses.
There exists a need to defend ships against low flying sea skimmer missiles such as those known as Exocet or Silkworm, or the like. Conventional radars have difficulty detecting such missiles because of the images or reflections that cause the signal return from the missile to fade in and out when the direct path and multipath signals reinforce or cancel each other. Conventional radars employ a long pulsewidth and typically have an instantaneous bandwidth on the order of 100 MHz. However, a radar that employs a train of short pulses on the order of 200 picoseconds having an instantaneous bandwidth on the order of 5 GHz is capable of separating the direct path return from the multipath return, thus allowing detection of low flying sea skimmer missiles. Furthermore, the wide bandwidth signal may enhance the signal return from a target having a low radar cross-section because of resonant scattering characteristics of the target over a wide frequency band. Thus, such a short pulse radar may also have potential application as an adjunct radar to existing ship air defense radars.
Impulse radars employing trains of short pulses are currently being investigated in research laboratories. These existing experimental radars typically take the approach of switching the RF transmit signal on and off in picoseconds to generate a train of extremely short pulses. Such radars require the impulse generator to have a peak power on the order of several megawatts due to the fact that it has a low duty factor in that the pulse width of the impulse generator is extremely short compared to the required interpulse period. On receive, an extremely wideband receiver is required to detect the entire bandwidth of the impulse. Hence, it is difficult to provide satisfactory gain in the receiver amplifier. Accordingly, there is a need for an improved impulse radar system.